zygote

Examples of zygote in the following topics:

• Fertilization

  • Fertilization is the process in which gametes (an egg and sperm) fuse to form a zygote.
  • A zygote that has more than two sets of chromosomes will not be viable; therefore, to ensure that the offspring has only two sets of chromosomes, only one sperm must fuse with one egg.
  • This process ultimately leads to the formation of a diploid cell called a zygote.
  • The zygote divides to form a blastocyst and, upon entering the uterus, implants in the endometrium, beginning pregnancy.
  • (a) Fertilization is the process in which sperm and egg fuse to form a zygote.

• Life Cycles of Sexually Reproducing Organisms

  • The zygote immediately undergoes meiosis to form four haploid cells called spores.
  • Fertilization between the gametes forms a diploid zygote.
  • The zygote undergoes meiosis to produce haploid spores.
  • Fusion of the gametes gives rise to a fertilized egg cell, or zygote.
  • The germ cells are generated early in the development of the zygote.

• Double Fertilization in Plants

  • Angiosperms undergo two fertilization events where a zygote and endosperm are both formed.
  • Of the two sperm cells, one sperm fertilizes the egg cell, forming a diploid zygote; the other sperm fuses with the two polar nuclei, forming a triploid cell that develops into the endosperm.
  • The zygote divides to form two cells: the upper cell (terminal cell) and the lower cell (basal cell).
  • In angiosperms, one sperm fertilizes the egg to form the 2n zygote, while the other sperm fuses with two polar nuclei to form the 3n endosperm.
  • After fertilization, the zygote divides to form an upper terminal cell and a lower basal cell.

• Cleavage, the Blastula Stage, and Gastrulation

  • A zygote undergoes rapid cell divisions (cleavage) to form a spherical ball of cells: the blastula; this will further develop into a blastocyst.
  • The development of multi-cellular organisms begins from a single-celled zygote, which undergoes rapid cell division to form the blastula.
  • During cleavage, the cells divide without an increase in mass; that is, one large single-celled zygote divides into multiple smaller cells.
  • Describe the events that occur from the formation of a zygote to gastrulation

• Reproductive Cloning

  • Sexual reproduction requires two cells; when the haploid egg and sperm cells fuse, a diploid zygote results.
  • The zygote nucleus contains the genetic information to produce a new individual.
  • If the haploid nucleus of an egg cell is replaced with a diploid nucleus from the cell of any individual of the same species (called a donor), it will become a zygote that is genetically identical to the donor.

• Human Gestation

  • Once the zygote implants in the uterine wall, embryonic and fetal development continue through three trimesters to birth.
  • When fertilized (at conception), the egg, now known as a zygote, travels through the oviduct to the uterus .
  • The outer layers of the zygote (blastocyst) grow into the endometrium by digesting the endometrial cells.

• Animal Reproduction and Development

  • This process produces a diploid fertilized egg called a zygote.
  • The process of animal development begins with the cleavage, or series of mitotic cell divisions, of the zygote .
  • Three cell divisions transform the single-celled zygote into an eight-celled structure.
  • During embryonic development, the zygote undergoes a series of mitotic cell divisions, or cleavages, to form an eight-cell stage, then a hollow blastula.

• Mosses

  • The zygote, protected by the archegonium, divides and grows into a sporophyte, still attached by its foot to the gametophyte.
  • After fertilization, the zygote divides and grows into a sporophyte, which stays attached to the gametophyte.

• Reproductive Isolation

  • Recall that a zygote is a fertilized egg: the first cell of the development of an organism that reproduces sexually.
  • A postzygotic barrier occurs after zygote formation; this includes organisms that don't survive the embryonic stage and those that are born sterile.
  • When fertilization takes place and a zygote forms, postzygotic barriers can prevent reproduction.

• Development of the Seed

  • In angiosperms, the process of seed development begins with double fertilization and involves the fusion of the egg and sperm nuclei into a zygote.
  • Right after fertilization, the zygote is mostly inactive, but the primary endosperm divides rapidly to form the endosperm tissue.
  • Sometimes each sperm fertilizes an egg cell and one zygote is then aborted or absorbed during early development.